Packed Bed Chemical Looping Platform: Design and Operation of 30 kWth Pilot Unit

Abstract

Chemical looping combustion is a novel flameless combustion, where the conventional combustion is divided into reducer and oxidizer with assistance of the oxygen carrier. Due to its instinctive CO2 separation, high efficient and environmental-friendly property, chemical looping combustion attains more concerns. Large-scale experimental unit is a vital to chemical looping combustion, especially the commercial development. The reactor configuration of the worldwide pilot units are fluidized bed or moving bed, and the pilot unit with packed bed has not been reported. In this study, the pilot scale chemical looping packed bed unit with a nominal thermal capacity of 30kWth is designed on the basis of previous laboratory scale investigation. The pilot unit includes four parts, which is gas system, reaction system, tail gas treatment and gas analysis system, and auxiliary electrical system. The pilot packed bed reactor is made from 310s stainless steel tube with a 0.089 m o.d., a 0.079 m i.d., and 2.0 m height. A K-type thermocouple with 13 measurement points is located at the center of the packed bed reactor to obtain the axial temperature profile. The packed bed chemical looping platform is constructed to demonstrate the feasibility of generating high purity hydrogen from syngas derived from biomass wastes with on-site carbon capture. Two testing runs were presented using 5mm × 4-6mm cylindrical oxygen carriers comprising of 50wt % iron oxide (Fe2O3). The pure CO and the mixture of CO and H2 with a flow of 15 SLPM are the fuels of the two tests. The first test resulted in a full CO conversion with a 25.0% conversion of the oxygen carriers during reduction, the production of 3.82mol hydrogen with an average purity of 98.0%, and the maximum temperature rise is 219K during air combustion. The second test leaded to a full fuel conversion with a 35.7% conversion of the oxygen carriers during reduction, the production of 4.67mol hydrogen with an average purity of 98.0%, and the maximum temperature rise is 290K during air combustion. The two testing runs, the first operation of packed bed chemical looping pilot unit, supported syngas-based chemical looping application for hydrogen and power co-generation with in suit carbon capture and also demonstrated the design of the 30kWth pilot chemical looping platform with packed bed reactor.